Method of speed regulation for polyphase induction motors



March '13, 1928. 1,662,549

. K. VON KANDO METHOD OF SPEED REGULATION FOR POLYPHASE INDUCTION MOTORS Fi1edvFeb.28. 1922 3 Sheets-Sheet 1 Inventqr Kalman .von Kando,

March 13, 1928. 1,662,549

K. VON KANDO METHOD OF SPEED REGULATION FOR POLXPHASE INDUCTION MOTORS Filed Febjg 1922 3 Sheets-Sheet 2 Inventor:

March 13, 1928. 1,662,549

- K. VON KANDO METHOD OF SPEED REGULATION FOR POLYPHASE INDUCTION MOTORS Filed Feb.28. 1922 3 Sheets-Sheet 3 FiG.3.

FiG.4.

Invento'r": Katman vo Kando,

Patented Mar. 13, 1928.

UNITED STATES PATENT OFFICE.

KALMAN voil KANDO, OF BUDAPEST, HUNGARY, ASSIGNOR TO WESTINGHOUSE ELEC- TRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

METHOD OF SPEED REGULATION FOR POLYPHASE INDUCTION MOTORS.

Application filed February 28, 1922, Serial No. 540,034, and in Hungary March 2, 1921.

My invention relates to a speed regulation for polyphase induction motors by means of changing the pole connections and employing all the coils of the winding in each ar- 6 rangement.

For the performance of the new speed regulation I use an n.8-pole threephase winding (n being any suitable integer) having in each phase for each pole one coil, each coil overlapping two coils of each of the two other phases. Such three-phase windings are termed three-range windings in distinction of the two-range windings having one coil for each pair of poles. The

invention is applicable to windings made up of single or multiple spiral or lap coils.

According to my invention the change of the pole number is effected by changing the winding in such manner, that the coils gether at one end whilst two of the resulting coil-groups consisting each of n3 colls O and spaced apart by g with respect to each other are connected to the two terminals of each phase of a four-phase current source, forming thereby an eight-phase winding with no poles.

It has been already proposed to transform an n.8 pole two-range three phase winding with one coil per pair of poles into an m6 pole two-phase winding for the pur' pose of changing the speed of induction motors in a ratio of 3 :4, but this method allows only this one relation, whilst the method according to my invention having for its base a doubled three-range n.8 pole three-phase windin allows the attainment of other speed relations beside the 3 4 ratio.

In the drawin s:-

Fig. 1 shows iagrammatically an 8-pole three-phase primary winding as applied to the rotor of an induction motor;

Fig. 2 shows the winding according to Fig. 1 connected for 6-pole eight-phase opertion;

Fig. 3 shows diagrammatically the connections of the coils in the 8-pole three-phase arrangement and Fig. 4 shows diagrammatically the connections of the coils in the 6-pole eightphase arrangement.

The changing of pole connections is performed in the primary part of the motor. In Fig. 1 the stator winding is not shown, but is similar to the primary or rotor winding, with the difference however that the terminals of the coils are connected to a. rheostat instead of being connected to the current source. As the primary winding is applied according to Fig. 1 to a rotor, the connections with the current source are established by means of sliprings and brushes. Of course the changing of pole-connections according to my inven tion can be performed also if the primary winding is on the stationary part of the motor, in which case the terminals are simple leads. According to Fig. 1 the motor is fed by means of a phase-converter, but can be fed of course from the secondary part of another induction motor connected in cascade with the first one and provided with the change of poles according to my invention.

Referring to the drawings I have shown a phase-converter P comprising a stationary iron body provided with a continuous secondary winding P from which the threephase terminals I, IV, VIII are branched ofi at spacing of 120, and further from which the so-called eight-phase terminals I, II, III, V, VI, VII, IX and X are branched oil at spacing of 45. The primary winding P is connected to a singlephase current source L, L, and a rotary field magnet M within the stator is energized by a direct current generator g.

The coils belonging to the three different phases of the primary Winding of the motor are lettered A A B B and C -C respectively.

As will be seen from Fig. 1, the threephase winding has per pole one coil overlapping two coils of each of the two other phases. The three coils A B and G which are spaced 120 apart are connected together at one end by the slip-ring 1. Similarly 100 the three coils A B (1 also spaced 120 apart are connected together by the slip-. ring 2. The other groups of three coils spaced apart by 120 are also connected respectively by the remaining slip-rings 3, 4,

ll ii in. the o-gole three-phase connection shown. in l and the threephase curent is tied :lrom the terminals is, il and iii of the pause-converter by means of switch 3 whilst the contacts oi the switch is, are interrupted. The direction oi the current at a given momentindicated in l in the coils oi phase A by arrows, pole being generated in the axis of each coil, thus forming 8 poles in all.

his to be seen in Fig. 3, the one end of all the coils belonging to the sonic phase of the three-phase winding are connected to a commen 1 base lead a, l), respectively, whilst one coil of each phase the other ends of spaced 120 apart are united by means of leads 1-8 respectively lorming neutral points, i

To change the connections to sir; poles, switch ll, is interrupted 2), and-the leads or slip rings l-8 are connected by means of 1 le S\ itch is, to'tlie tour-phase terminals ll, ill, H, V, i l, l lil, Hi and K of the phase-converter P respectively, whilst the slip rings a, 7), 0 term the neutral points, as clearly seen th diagram or connections shown in Figure The one group a G shown with full lines is co ncctcd to the one terminal l: oil the phase .sll l. The second terminal VI of the same phase connected by means of the slip ring 5 to the group of coils A,, B C and disposed 60 away from the corresponding coils oi? the first group The direction of thecurrents at a given moment in the coils of this phase as well as the poles generat by these currents are indicated by arrows in. Zig. 2, lit is to be seen, that a regular fi-pole field results.

in the same manner the two groups of coils A7,, B hi and A B C are connected together at one end by means of the rings 2 and 6 respectively to the phase ill- VH; the coils A .213 U, andi i B C are connected by means of the rings. and! respectively to the phase J: and tno coils A B U, and A C are connected by means of the at and 8 respectively to the phase V Each of the four phases contains one- -lourth of the total nruuber of coils, conditions being similar in each phase except for a ase displacement oi? corresponding our-phase rotarydield, an nil-pole three-phase winding those 120 coils which spaces apart an angle oi instead of 120 are connected together in the above described manner forming. groups, and

phase, s

. d has the ad outage that an -ph winding, which can be changed according to my invention into an viii-pole winding, may be changed by the methods disclosed in my application Serial l lo. 523,526 filed December 19, 19:21 into a l2-pole twophase winding. To this end the rings 1 and 5 are connected to'the terminal )5 of the pliaseconverter and the rings 3 and 7 tot-lie terminal Vl o'i thissame phase, while the rings 2,6 and 4, 8 respectively are connected to the two terminals ill and IX oi the phase spaced 90 apart. Thus the same winding allows two diil'erentpole numhers to. be obtained.

Claims: p

i. The combination with an induction motor having a three-phase winding with n' 8 poles, Where a is an integer, with one coil in each phase for each pole, and each coil overlapping two coils of each of the other phases; of a source of three-phase current and a source of so-called eight-phase current; means including switch mechanism for connecting one end of all of said coils in n 3 groups to the'respective terminals of said three-phase current source, the coils in each group being or the same phase, or for connecting the other ends of all of said coils in n 8 groups spaced /71 degrees apart to each of the two terminals of each phase of said eight-phase current source, each of said last mentioned groups consisting of n 3 coils of different phases spaced apart 120/1 degrees. 7 I

2. An induction motor provided with a three-phase winding having np 8, poles, where n is an integer, with one coil in each phase for each pole and eachcoil overlapping two coils of each of the other two phases; a ter minal member connected to oneend of all the coils of one phase, a second terminal member similarly connected to all the coils of another phase, and a third terminal member similarly connected to all the coils'of the remaining phase; eight other terminal members, and a connection between the last namedtcrminal members respectively and the other ends of the coils belonging to different phases and spaced apart IQO/n degrees. I i

I 3. A polyphase induction motor having a three-range winding witheach coil overlapping two coils of the other two ranges, one end of all the coils being united into n 3 groups, where n is an integer, and the other ends oi the I coils belonging to different groups being united into n 8 groups, and insane for connecting saidgroups either by their n 3 ends to a polyphase alternating source with an odd number of phases or by their n 8 ends to a polyphase current source with an even number of phases.

4. A ,polyphase induction motor having a three-range windingcomprising n 24 coils, a being an integer, each coil overlapping two coils'ot the other two ranges, the coils being arranged in eight groups, each group containing three coils spaced apart 120/1 degrees, the coils of the respective groups being united at one end and connected to separate current leads, current leads the number of which is a multiple of three connected to the other ends of the coils, said last mentioned current leads each being connected to the same number of coils belonging to the same range of the Winding.

5. A polyphase induction machine having a multiple-pole-number primary winding adapted to operate on different pole numbers and different phase numbers including three phases and eight phases, said Winding having the following elements or duplicates thereof, to Wit: a three-phase winding with eight poles, with one coil in each phase for each pole, and each coil overlapping two coils of each of the other phases, one end of all of said coils being connected in three groups to the respective three phase-terminals, the other ends of all of said coils being connected in eight groups to the respective eight-phase terminals, each of said last mentioned groups consisting of three symmetrically spaced coils, one from each of the three phases.

In testimony whereof I afiix my signature.

KALMAN VON KANDO. 

